The solution

Then, from the “Project Structure” dialog, choose the “Modules” item in the left pane [1], then the “Dependencies” tab [2]. Now choose the + symbol on the right hand side of the dialog [3] and choose the “1 JARs or directories…” option [4].

Now, navigate to the path of your groovy library such that the path of your import statement …:

…can be found immediately within the folder you select:

Finally, you will be prompted to choose what type of thing you’re linking to and you should select “Classes”:

Now you can “ok” your way back through the 2 dialogs and your project should build.